VoIP Voice and Fax Signal Processing

2.3 NETWORK AND ACOUSTIC INTERFACES FOR VoIP

Internet connectivity is the main requirement for VoIP. This connectivity is achieved through LAN or WAN interfaces. WAN interface directly goes to the Internet service provider. The popular WAN interfaces available to the residential user are DSL, cable, worldwide interoperability for microwave access (WiMAX), and direct dial-up. LAN interfaces are used with existing home or office network or with existing DSL and cable modems. Some of the popular LAN and WAN interfaces used with VoIP services are listed below:

1. Ethernet LAN interface available in residential, office, and public places
2. USB as a LAN interface
3. Bluetooth as a LAN interface
4. WLAN as a LAN interface
5. WiMAX as a direct WAN interface
6. Direct WAN interfaces used with DSL service
7. Cable modem interface used as WAN interface
8. Dial-up modem along with PC creates network connectivity as a low-bandwidth WAN

Acoustic interfaces for VoIP vary widely and are difficult to classify. VoIP service is used from multiple general-purpose computers, VoIP adapters, and residential gateways. Users will be hearing the voice through several acoustic interfaces. Some of the popularly used interfaces for user acoustics are follows:

1. Regular plain old telephone service (POTS) telephones connected to VoIP adapters
2. Fax machines connected to VoIP adapters also work for voice calls
3. IP phones connected on LAN interfaces
4. WiFi phones mainly used on a wireless LAN interface
5. USB handset phones connected to a ...